Composition containing surface-esterified siliceous solid and silicone oil



COMPOSITION CONTAINING SURFACE-ESTERI- FIED SILICEOUS SOLID AND SILICONEOIL Ralph K. Iler, Brandywiue Hundred, Del., assignor to E. I. du Pontde Nemours and Company, Wilmington, Del., a corporation of Delaware NoDrawing. Application April 1, 1952, Serial No. 279,908

Claims. (Cl. 25228) This invention relates to novel compositionscomprising an estersil and a silicone oil, and in a preferred aspect isdirected to lubricating compositions Which are ter-insoluble lubricatingThis application is oil.

a continuation-in-part of my copending United States applications SerialNo. 171,760, filed July 1, 1950, now abandoned, and Serial No. 191,717,filed October 21, 1950, now U. S. Patent No. 2,676,148. In the formerapplication I have described certain compositions containing estersils,a novel class of surface-esterified, supercolloidal, particulatesiliceous materials disclosed and claimed in my United Statesapplication Serial No. 171,759, filed July 1, 1950, now abandoned. Moreparticularly, an estersil is an organephilic solid in a supercolloidalstate of subdivision, having an internal structure of inorganicsiliceous material with a specific surface area of at least 1 m. /g.,having chemically bound to said internal structure -OR groups wherein Ris a hydrocarbon radical, wherein the The present application isdirected greases which are adapted for use under conditions requiring ahigh degree of resistance to deterioration by water.

A grease is ordinarily made by thickening a lubricating oil with athickening agent such as a soap. Greases made with many suchconventional thickeners are quite sensitive to moisture and at highrelative humidities, even though no liquid water may be present, showsigns of deterioration. Lack of water resistance is manifested bysuchchanges as loss of clarity, thinning of the grease upon standing incontact with high relative humidity, and actual separation of oil andthickening agent. When the latter change occurs the grease loses bodyand becomes practically valueless for its intended purposes.

By using an estersil as the thickening agent for a lubricating oil asdescribed in my above-mentioned application Serial No. 191,717, greasesare produced which are resistant to high relative humidities. They canbe stored for long periods in water-saturated atmospheres withoutshowing signs of deterioration and can therefore be said to have waterresistance. other hand, there are extreme conditions of use, such as inthe lubrication of bearings ening ordinary lubricating oils withestersils do not have the desired degree of water resistance.

Now according to the present invention I have found that silicone oilscan be thickened with estersils to give be imparted to an ordinaryfinely divided, non-esterified siliceous thickener by adding a siliconeoil thereto. Likewise, a grease made with nonesterified silica andsilicone oil together with another lubricating oil such as hydrocarbonoil is similarly lack- THE ESTERSIL Estersils suitable-for use in thecompositions of the have a specific surface area of as little as 1 m./g., it is preferred to use estersils in which the substrate has aspecific surface area of at least 25 mF/g.

1. The substrate The materials used to form the structure, thesubstrate, of the estersils used in the compositions and methods of theinvention are solid inorganic siliceous materials. They containsubstantially no chemically bound organic groups. They have reactivesurfaces which I believe to result from surface silanol (SiOH) groups.The substrate materials can be mineral or synthetic in origin. They canbe amorphous silica. They can be water insoluble metal silicates. Theycan be water insoluble metal silicates coated with amorphous silica.

The substrate particles are aggregates of ultimate units; they have atleast one dimension of at least millimicrons, thus they are in asupercolloidal state of subdivision. Preferably the substrate particlesare cojoined in very size) are preferred. Prefhave an average diameterof at least 1 micron.

Preferably, the inorganic siliceous solids used are porous, that is,they have exposed surfaces in the interior of the particle which areconnected to the exterior so that liquids and gases can penetrate thepores and reach the exposed surfaces of the pore walls. In other words,the solid forms a three-dimensional network or webwork thru which thepores or voids or interstices extend as a labyrinth of passages or openspaces.

Especially preferred are porous inorganic siliceous solids havingaverage pore diameters of at least four millimicrons.

The substrate particles have large surface areas in relation to theirmass. The term used herein and the one normally so used in the art toexpress the relationship of surface area to mass is specific surfacearea. Numerically, specific surface area will be expressed in squaremeters per gram (m. /g.).

According to the present invention, the substrate particles have anaverage specific surface area of at least 1 m. g. and, preferably, thespecific surface area is at least 25 m. g. and still more preferably 200m. g. In the case of precipitated amorphous silica, a preferredsubstrate material, there is an optimum range of about 200 to 400 m. g.Very voluminous siliceous aerogels having surface areas as great as 900m. /g., and preferably from 200 to 90O rn. /g., are very suitable foruse as substrate materials because of their greater thickeningefiiciency.

Specific surface area, as referred to herein, is determined by theaccepted nitrogen adsorption method described in an article A new methodfor measuring the surface areas of finely divided materials and fordetermining the size of particles by T. H. Emmett, in Symposium on NewMethods for Particle Size Determination in Sub-Sieve Range, published bythe American Society for Testing Materials, March 1941, page 95. Thevalue of 0.162 square millimicron for the area covered by onesurface-adsorbed nitrogen molecule is used in calculating the specificsurface areas.

Pore diameter values are obtained by first determining pore volume fromnitrogen adsorption isotherms, as escribed by Holmes and Emmett inJournal of Physical and Colloid Chemistry, 51, 1262 (1947). From thevolume figure, the diameters are obtained by simple geometry assumingcylindrical pore structure.

Determinations of gross particle size and shape of sub strate materialare suitably made by a number of standard methods whose choice for usein a particular case depends upon the approximate size and shape of theparticles and the degree of accuracy desired. Thus for coarse materials,the dimensions of individual particles or coherent aggregates can bedetermined with the unaided eye and ruler or calipers. For more finelypowdered material, the light microscope is used with a calibrated scale.For material having a particle size in the range of from 2 or 3 micronsdown to 5 millimicrons, the electron microscope is used. Particle sizedetermination using an electron microscope is described in detail by J.H. L. Watson in Analytical Chemistry, 20, page 576 (June 1948).

While various inorganic siliceous solids having the aforementionedproperties can be used as substrate materials in preparation ofestersils for use in the oil-grease compositions of the invention,precipitated amorphous silica is especially preferred. Such silica ischaracterized by X-rays as lacking crystalline structure.

The preferred amorphous silica consists of coherent aggregates ofnon-porous ultimate units in which the ultimate units are quite uniformin size and have an average diameter of to 100 millimicrons. Suchcoherent aggregates have a relatively loose structure and contain poresof at least 4 millimicrons average diameter as determined by nitrogenadsorption curves. The large pores afford easy access by alcoholmolecules in the subsequent esterification to give estersils.

The preparation of a variety of suitable amorphous silicas isillustrated in the examples. For a detailed discussion of sources ofamorphous silica for use in preparing estersils, reference should be hadto my copending application Serial No. 171,759, filed July 1, 1950.

Instead of silica, water-insoluble metal silicates can be used as thesubstrate. Such metal silicates can be prepared, as is well known in theprior art, by treatment of silicas with metal salts or hydrous metaloxides, excluding those containing only alkali metal ions. Such metalsilicates can be prepared so as to have a large number of silanol(-SiOH) groups on the surface of the particles. Thus metal silicateshaving a large proportion of meta ions on the surface may be activatedfor esterification by Washing with acids to remove a portion of themetal ions and leave surface silanol groups.

Crystalline metal silicates occurring in nature can also be used.However, the proportion of silanol groups on most minerals is very smallsince the surfaces also contain metal hydroxide groups, silicon oxygengroups and adsorbed metal ions. Therefore is necessary to introducesilanol groups on the surface. Loosely adsorbed metal ions may beexchanged for hydrogen ions by washing with dilute acids, or bytreatment with ion exchange resins. In some cases, more vigoroustreatment, such as reaction with acids at low pH and often at elevatedtemperatures are required in order to give a material which will containa sufficient number of silanol groups in the surface to yield anorganophilic product on esterification.

Alternatively or additionally, silanol groups can be introduced on thesurface of metal silicates by coating them with a layer of amorphoussilica. This is accomplished by treating, say, sodium silicate with anacid in the presence of the mineral silicate particles under suchconditions that the silica formed will deposit as a coating on themineral particles. Such methods are illustrated in the examples of myaforementioned copending application on estersils.

Mineral crystalline silicates which can be used in preparing thesubstrate particles are: the asbestos minerals, such as chrysotilcasbestos and serpentine (hydrous magnesium silicates), and amphiboles,such as crocidolite asbestos (a sodium magnesium iron silicate), amosite(an iron silicate), trcmolite (a calcium magnesium silicate), andanthothyllite (a magnesium iron silicate); clay minerals, such ashalloysite (an aluminum silicate), attapulgite (a magnesium aluminumsilicate), hectorite (a magnesium lithium silicate), nontronite (amagnesium aluminum iron silicate); kaolines, such as kaolinite, nacrite,and dickite (aluminum silicates), and bentonites, such as, beidillite,saponite, and montmorillonite (magnesium aluminum iron silicates); andmicaceous minerals, such as, phlogopite (a potassium magnesium aluminumsilicate), muscovite (a potassium aluminum silicate), biotite (apotassium iron aluminum silicate) and vermiculite (a hydrous magnesiumiron aluminum silicate).

2. The esterifying agents The inorganic siliceous solids described aboveare reacted with primary and secondary monohydric alcohols to give theestersils used in the compositions of the invention. Such alcohols,called represented by the formula ROI-I where R is an hydrocarbonradical wherein the carbon attached to oxygen is also attached to atleast one hydrogen atom.

Examples of compounds of this class are: Normal straight chain alcohols,such as ethyl, n-propyl, n-butyl, n-pentyl (amyl), n-hexyl, n-heptyl,n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl (lauryl), n-tetradecylmyristyl), n-hexadecyl (cetyl), n-octadecyl (stearyl); branched chainprimary alcohols such as isobutyl (Z-methyl-l-propanol), isoamyl(3-methyl-l-butanol), 2,2,4,trimethyl hexane-l-ol and 5,7,7,trimethyl,2(1,3,3-trimethyl butyl)octane-l-ol; secondary alcohols such asisopropyl, sec.-butyl (Z-butanol), sec.-amyl (2-pentanol), sec.-n-octyl(methyl hexyl carbinol or 2-octanol), methyl isobutyl carbinol, anddi-iso-propyl carbinol (2,4-dimethyl pentane-3-ol); alicyclic alcoholssuch as cyclopentanol, cyclohexanol, cycloheptanol (suberol), andmenthol; alcohols having ethylenic unsaturations such as allyl(Z-propene-l-ol), crotyl (Z-butene-l-ol), oleyl (cis-9-octadecen-1-ol),citronellol (3,7-dimethyl-6 (or 7) octen-l-ol), and geraniol(3,7-dimethyl-2,6-octadien-l-ol); compounds having acetylenicunsaturation such as propargyl alcohol (2-propyn- 1-ol); and aromatic(araliphatic) alcohols such as benzyl (phenyl carbinol),beta-phenyl-ethyl (2-phenyl-ethanol), hydrocinnamyl(3-phenyl-l-propanol), alpha-methyl-benzyl 1S1 -phenyl-ethanol), andcinnamyl (3-phenyl-2-propene- The saturated aliphatic primary andsecondary alcohols are preferred. In other words, the preferred estergroup is alkoxy.

The saturated primary aliphatic alcohols are especially preferredesterifying agents because they react more readily with the inorganicsiliceous materials at lower temperatures than do the secondary alcoholsand are more stable than the unsaturated alcohols at the temperature ofthe reaction.

The unsaturated alcohols, especially those containing one or more triplebonds or multiple double bonds are difiicult to use because of theirinstability. While many f the U saturated alcohols which are notparticularly before esterification, 1t

the esterifying agents, are 1 unstable under the those alcohols WhIChare known otherwise decompose under the conditions of temperature,pressure, etc. of the esterification obviously should be avoided.

Technically, there is no upper limit to the number of carbon atoms veryrapidly in the standard humidity The esterifying agent need not beMixtures of alcohols can be used. ture of. isobutyl and sec-butylalcohol can be used. Also, there can be used a mixture of differentchain lengths in technical grades of lauryl alcohol made from cocoanutoil (Lorol), technical oleyl alcohol made from lard, and technicalstearyl alcohol made from tallow.

3. Esterification Metal atoms on the surface of metal silicates must beexchanged for hydrogen atoms. This can be done by treatment with ahydrogen form of a cation exchange resin or by treatment with an acid asmentioned heretofore. tively, the particles can be coated with a thinlayer of silica, the external surface of which can then be reacted withalcohol.

The inorganic siliceous solid is preferablyfreed of extraneous materialbe ore esterification and the pH is adjusted to avoid strong acids oralkalies in the reaction. The pH range is preferably to 8.

The amount of water present in the reacting mass duriug theesterification step has an important bearing on the degree ofesterification that will be attained.

In order to esterify sufliciently to obtain organophilic surfacemodified siliceous products, the water in the liquid phase of the systemshould not exceed 5% of that phase for a hydrophobic, the water contentshould not exceed about 3%. For maximum esterification, the Watercontent must be kept below about 1.5%; in fact, it is desirable to keepthe water content as low as possible.

Because of the hindering effect of water on the esterification. if thesiliceous solid to be esterified is wet, the free water must be removedeither before the solid is put into the alcohol or alternatively it maybe removed by distillation after mixing with the alcohol.

Simple air drying at temperatures from 100 to 150 C. free water. Dryingmay be of vacuum. For many types not satisfactory prior toesterification by azeotropic distillation. Thus, water-wet cake can bemixed with a polar organic solvent such as methyl ethyl ketone and themixture distilled until the system is freed from water. The organicsolvent can then be evaporated to give a dry product for reaction withalcohol.

Alternatively, esterifying agent alcohol should be present in suflicientexcess to facilitate sufiicient alcohol portions of alcohol must be usedwhen no Water is removed from the system during the reaction, since thereaction liberates water and may exceed the maximum permissible valueunless alcohol is added either before or during the reaction step.

When operating at atmospheric pressure, the preferred procedure is toremove water continuously by azeotropic distillation during thereaction. Using this method, it is not necessary to use as large anexcess of alcohol as when no water is removed during the reaction.

The esterification reaction is carried out at an elevated temperature.The extent of the reaction is fixed more by the temperature than by thetime, that is, at a suitable temperature, the reaction proceeds quiterapidly up to a certain point which is characteristic of the temperatureand of the alcohol and given temperature than secondary alcohols. Thefollow ing table indicates the temperature required for the preparationof a given type of estersil within a practical reaction time such as oneor two hours. While it is difficult to Primary Secondary EstersilProperty 1 Alcohols, Alcohols, degree O. degree 0. N a OrganophilicHydrophobic 118 225 Zero Methyl Red dye adsorption. 1190 275 M l Themeaning and significance of these properties will be discussed in latersections.

Temperatures substantially below about 100 C. are unsuitable. Alcoholcan be adsorbed on the siliceous surfaces at such temperatures but trueesterification is not obtained.

The esterification temperature should not exceed the thermaldecomposition Alternatively, the alcohol by applying vacuum to thereaction vessel. Or where the alcohol is one which will distill atatmospheric pressure without decomposition, simple distillation can beused. In the case of higher alcohols which are not readily distilled,except under very high vacuum, the

may be vaporized with a low chloroform,

4. Properties of the estersils The esterified inorganic siliceoussolids, the estersils, are in the form of powders or sometimes lumps orcakes which are pulverable under the pressure-of the finger or by alight rubbing action. They are generally exceedingly fine, light,fluffy, voluminous powders.

The light, fluffy nature of the preferred estersils can be expressed bythe characteristic of bulk density. For ease in dispersion, theestersils preferably used in thickening lubricating oils to obtain theoil and grease compositions of the present invention are those having abulk density not greater than 0.20 gram per cubic centimeter under acompressive load of 3 lbs/sq. inch, and not greater than 0.30 g./cc. at78 lbs/sq. inch. However. in certain cases, it may be desirable to usehigher bulk density material to facilitate handling The bulk densityunder compressive load of 3 p. s. 1. is determined by placing a weighedamount of powdered estersil in a vertical glass tube which is one-halfinch in diameter, ten inches long, and is fitted with a flat frittedglass bottom. A fritted porous glass plug is then rested on top of thepowder in the tube. A steel rod weighing about 0.6 lb. is then rested onthe glass plug to provide the pressure of 3 lbs/sq. inch. The volume ofthe estersil is then measured and the bulk density calculated bydividing the known weight (in grams) of the estersil by the measuredvolume (in cc.) of the estersil at compression equilibrium.

In measuring the bulk densities of the siliceous materials under acompressive load of 78 p. s. i., a weighed accurately machined, hollowsiliceous steel plunger by means of a hydraulic Carver laboratory press.The pressure is slowly increased to the desired point and thedisplacement of the plunger is measured by means of a eathetometerreading to of a millimeter. From the known constants of the instrumentthe volume of the silica under the equilibrium pressure may becalculated. The density is then calculated from the known weight andvolume as described above.

The esterifieation reaction does not substantially change the structureof the inorganic siliceous solid or substrate which was esterified. Inother words, the internal structure of the estersil, the structure towhich the OR groups are chemically bound, has substantially the sameparticle size, surface area, pore diameter, and other characteristicsdescribed previously in the discussion of the substrate material. Theestersil particles are in a supercolloidal state of subdivision.

All the estersils used in the compositions and methods of the inventionare organophilie. By organophilie, I mean that when a pinch of theestersil is shaken in a two-phase liquid system of water and normalbutanol in a test tube, the estersil will we into the n-butanol phase inpreference to the water phase. In contrast, the unesterified inorganicsiliceous solids are not organophilic; when tested in the above manner,they prefer the water hase.

p In order to make an inorganic siliceous solid organophilic, it isnecessary to react a certain minimum proportion of the surface silanolgroups with an alcohol containing at least 2 carbon atoms. With mostalcohols, the esterified material becomes organophilic when it containsmore than about 80 ester groups per 100 square millimicrons of surfaceof the internal structure or substrate. The products are markedlyorganophilie when there are chemically attached more than about 100ester groups per 100 square millimicrons of substrate surface.

Estersils, tho organophilic, are also hydrophilic unless more highlyesterified. Thus while they prefer normal butanol to water in abutanol-water system, they will in the absence of an organic phase wetinto water also. The preferred estersils, however, are those which aremore highly esterified so that they are not only organophilic but arealso hydrophobic, that is, they will not wet into water even in theabsence of an organic phase. Such organophilie and hydrophobic productsare obtained by esterifying the inorganic siliceous material to give anestersil containing at least 20 ester groups per I square millimicronsof substrate surface.

Hydrophobic estersils can be made without esterifying all the surfacesilanol groups. However, in order to obtain estersils having maximumstability toward hydrolysis, it is necessary that the ester groups becrowded together so closely on the surface that the surface iscompletely protected. For most ester groups, especially for thosecontaining 3 to 6 carbon atoms, this requires at least about 270 estergroups per square millimicrons. When such a completely protected surfacehas been obtained, the specific hydroxylated surface area, as measuredby the methyl red dye adsorption test described below, in zero; in otherwords, essentially no methyl red dye will adsorb on the surface of theestersil.

In the case of the preferred alcohols, those containing 3 to 6 carbonatoms, it is possible to force far more than 270 alcohol molecules, say300 to 400, to react per 100 square millimicrons of surface area of thesiliceous substrate by using more severe reaction conditions, care beingtaken not to decompose the alcohol or resulting ester groups. Suchproducts not only adsorb essentially no methyl red dye but exhibitoutstanding stability toward water and certain other chemicals. Forexample greases prepared from certain of such estersils and mixed in theratio of 9 to 1 with conventional calcium soap greases do notdisintegrate but show excellent water resistant properties in a 7-daystorage test at 210 F. and 100% relative humidity.

The methyl red adsorption test is carried out by agitating in 25 cc. ofan anhydrous benzene solution containing 0.6 to 0.7 gram of the acidform of methyl red per liter, a suspension of a few tenths of a gram ofthe dried silica or estersil sample to be tested. No more than about 0.7g. of the sample should be used in the test, and appreciably less mustbe used with voluminous samples to avoid getting a mixture too thick tohandle. Within the latter limitations, however, the amount of sampleused should provide, as near as possible, a total hydroxylated surfacearea of 10 m? in the test.

The test mixture is agitated for about two hours at about 25 C. to reachequilibrium conditions; an equilibrium concentration of 400 milligramsof dye per liter insures saturation adsorption. The decrease in dyeconcentration in the benzene solution is determined by adsorptionspectrophotometric observations at 4750 A of both thg original andequilibrium benzene solutions of methyl re The specific hydroxylatedsurface area in m. /g. is calculated from the formula Grams dye adsorbedX fiogrjdros No. 1l6 lO Grams silica employedXmolecular weight of methylred where C is the weight of carbon in grams attached to 100 grams ofsubstrate, n is the number of carbon atoms in the OR groups, Sn is thespecific surface area in m. /g. of the substrate as determined bynitrogen adsorption.

Where the sample to be analyzed is one in which the type of alcohol isunknown, the sample can be decomposed with an acid and the alcohol canbe recovered and identified. The specific surface area of the substratecan be determined by first burning off the ester groups as, for example,by slowly heating the estersil in a stream of oxygen up to 500 C. andholding it there for about 3 hours and then rehydrating the surface ofthe particles by exposure to 100% relative humidity at room temperaturefor several hours, and finally determining the surface area of theremaining solid by the nitrogen adsorption method.

In estersils, the OR groups are chemically bound to the substrate.Estersils should not be confused with compositions in which alcohol ismerely physically adsorbed on the surface of a siliceous solid. Adsorbedalcohols can be removed by heating the material at relatively lowtemperatures, for example, C. under high vacuum, for example, 10' mm. ofmercury, for one hour.

In contrast, estersils are stable under such treatment. Neither can theOR groups of estersils be removed by washing with hot methyl ethylketone or similar solvents or by prolonged extraction in a Soxhletextractor. In the case of ordinary physical adsorption, the alcohol isdisplaced by such treatment.

THE SILICONE OIL The silicone oils used with of this invention arewater-insoluble, substantially nonpresent, are the types most widelyavailable and have the lowest cost, and are preferred. Of the availablesilicone oils molecular weight are preferred because volatility, sincethe compositions of the wide use at elevated temperatures.

Examples of particular silicone oils which may be used are thepolymethyl siloxanes having a viscosity of over 50 centistokes at 25 C.and polymethyl phenyl siloxanes Dow Corning DC550 silicone oil). Anothercommercially available material is known as General Electric SiliconeOil No. 9981.

The silicone oils, although of only relatively recent commercialimportance, are well understood in the art, being described, forinstance, in chapter 4 of Chemistry of the Silicones G. Rochow, 1st Ed.,1946, and further described in chapters 5 and 6 of the 2nd ediin 1951.The alkyl, aryl, and alkyl-aryl silicones mentioned as oils in thesechap ters are suitable for use with estersils according to the presentinvention.

THE ESTERSIL-SILICONE OIL COMPOSITIONS The estersil-silicone oilcompositions of this invention of their lower invention find dominantcomponent, ring the estersil into a quantity of the liquid silicone. Onthe other hand, if the estersil is the predominant ingredient, thesilicone may be sprayed onto the estersil in a tumbling barrel or thesilicone oil may be diluted with a solvent such as toluene or benzene,and the estersil added to the diluted solution followed by evaporationof the solvent.

Compositions of great usefulness are obtained throughout the entirerange of estersil-silicone oil proportions. Compositions in which theestersil is present in predominating proportion appear as dry,free-flowing powders, due to the ery high absorptive capacity of theestersil Such compositions have major utility as commonly encountered inchemical apparatus such as in dryers. The action of the estersil inthickening the grease is pronounced even with small amounts, andexcellent greases have been made using from 5 to 25% of estersil.

It will be noted that the mixing of a silicone oil and an estersil tomake a grease may be carried out in a manner which has heretofore beenused for introducing other non-soap thickeners into oil. It is wellunderstood in the grease-manufacturing industry that mixing is importantand that thorough dispersion of the thickening agent is essential. Paintmills, ink mills, colloid mills, mixers of the sigma-arm type, andsimilar devices may be used to disperse estersils in the silicone oil.

The degree of water resistance of a grease may be demonstrated byplacing a sample of th THE OTHER LUBRICATING OIL Now while estersils areexcellent thickeners for silicone oils and the resultingproducts arehighly useful as above just been made, Oils which contain, say, 5 to 10%of a water-soluble component or which are themselves soluble to thatextent in water can be classed as essentially water-insoluble oils.However, to obtain maximum In general, any water-insoluble animal,vegetable, mineral, or synthetic chemical having oil characteristics andlubricating or friction-decreasing properties can be used.

Illustrative of teristics such as di(2-ethyl hexyl) adipate, bis-nonylglutarate, di(2ethyi hexyl)th1opropionate, di(2-ethyl hexyl)oxydibutarate, propylene oxide-tetrahydrofuram copolymer, di(2-ethylhexyl)sebacate; and dimethyl cyclohexyl phthalate.

The choice of a water-insoluble lubricating oil to be used is, ofcourse, b d on a consideration of the reof application of the finishedThe considerations are analogous to those an oil to be used withconventional soap thickeners. For example, illustrative of matters to beconsidered in are cost, maximum and oxidation stability, operation,chemical sign.

Thus, low cost would be a reason for choosing a petroleum oil of naturalorigin. Such oil is suitable for most common uses where extremeconditions are not encountered. If low temperature operation weredesired, then low pour point, low viscosity, naphthene base leum oils,or synthetic di-ester, or

temperature, power consumption during bearing reactivity, and bearmgenclosure deered where product is to be used in corrosive chemicalsurroundings. Low viscosity oils are favored for use in bearings wherelow power consumption is desired and conversely high viscosity oils arefavored where there compositions obtain- THE ESTERSlL-SILICONEOIL-LUBRICATING OIL COMPOSITIONS The estersil-in-silicone oilcompositions containing another lubricating oil have propertiesresembling the twocomponent estersil-silicone compositions alreadydescribed, in that they are water resistant and in certain proportionsare highly useful greases. However, they have the advantage ofinherently low cost and may possess better lubricating characteristicsif the added lubricating oil is superior in this regard to the siliconeoil.

Again in the three-component system the proportions of ingredients maybe widely varied. Considerations already noted for the two-componentsystem may likewise apply to the three-component system-for instance,when a relatively large proportion of the dry powdered estersil is mixedwith relatively small proportions o silicone oil and the otherlubricating oil compositions are obtained which can subsequently bediluted out with additional lubricating oil to give excellent greases.Similarly, it will ordinarily be desirable that the silicone oil bepresent in a lesser proportion than the estersil.

More particularly, the exact proportions of estersil, silicone oil, andother oil will be determined by the properties which are desired in thecompositions comprising the three components. If a very highly waterresistant grease is desired, the amount of silicone oil used will belarger than otherwise. If a very thick grease is desired, the proportionof estersil will be larger than for a thin grease. If a very low-costgrease is desired, the proportion of lubricating oil such as hydrocarbonoil will be as high as possible, commensurate with the degree of waterresistance and amount of thickening desired.

It should be observed that estersils are a class of materials in whichthe individual members of the class may diifer considerably as to suchproperties as surface area and pore diameter. These properties affectsubstantially the thickening efficiency of the particular estersil. Forinstance, estersils of high specific surface areas are found to beconsiderably more effective as thickeners than those of low specificsurface area. In speaking of the proportions of the ingredients in acomposition of this invention, therefore, it is convenient to relate theproportioras to the specific surface area of the estersil being use Nowalthough it is possible to improve the water resistance of hydrophobicestersils in organic systems by mixing them with as little as 1 to 2parts by weight of polysiloxane per 100 parts by weight of hydrophobicestersil per 100 m. g. of estersil surface, it is preferred to employ atleast 3 /2 to 4 parts by weight of polysiloxane per 100 parts by weightof hydrophobic estersil per 100 m. g. of estersil surface to achieve aproduct which will yield highly water resistant compositions uponincorporation into such organic systems as lubricating oils. Since theuse of more than parts by weight of polysiloxane per 100 parts by weightof hydrophobic estersil per 100 m. g. of estersil surface will cause nosubstantial improvement in water resistance and will, in general, addgreatly to the cost of the composition, this amount of polysiloxane isthe preferred upper limit in compositions of the invention. In general,using hydrophobic estersils having specific surface area of 25 to ,100m. /g., from 20 to 40% by weight of hydrophobic estersil is required togive a medium grease consistency with a Mid-Continent solvent-treatedpetroleum oil. In contrast, the same grease consistency is obtained withthe same oil using from 4 to 25% by weight, of those hydrophobicestersils having substrates withtspecific surface areas of 200 to 900 m.g.

The manner of mixing the compositions containing the estersil, siliconeoil, and another oil is similar to that already described for theestersil-silicone oil mixtures. It will be understood that in greaseswhere a large proportion of hydrocarbon oil is used, the intense mixingof the silicone oil and estersil, with or without a small amount ofhydrocarbon oil, may be first carried out and this mixture may then bediluted out with the hydrocarbon oil until the desired consistency isreached.

Using a hydrophobic estersil having a specific surface area of 260 m./g., a substrate of amorphous silica consisting of a loose network ofnon-porous ultimate units, pores of at least 4 millimicrons averagediameter, and esterified with n-butanol so as to contain 370 butoxygroups per square millimicron of surface, it is particularly preferredto use about from 9 to 11 parts by weight of polysiloxane (silicone) oilper 100 parts by weight of hydrophobic estersil to achieve a productwhich will yield highly water resistant compositions upon incorporationinto such organic systems as hydrocarbon lubricating oils to makegreases.

The invention will be better understood by reference to the followingillustrative examples in addition to those already given.

Example 1.-A of an estersil was made One volume of a solution of 0.48 Nsulfuric acid was added at a uniform rate, over a period of 30 minutes,at a temperature of about 30 C., to three volumes of a solution ofsodium silicate, containing 2% SiOz and having a molar SiOzzNazO ratioof 3.36. The amount of sulfuric acid solution was adjusted so that itwas equivalent to 80% of the NazO in the original sodium silicate. ThepH during this process dropped from 11.3 to about 9. Violent agitationwas provided to insure complete and instantaneous mixing. Thetemperature during the entire reaction was maintained below 40 C. Thesodium ion concentration remained below 0.3 N throughout the process.The clear sol resulting from this process step and containing 1.5% SiOz,is called the heel. This clear sol contains extremely tiny, discreteparticles of silica. These particles are near the lower limit ofcolloidal dimensions and are so small that the solution remains almostwater clear (only slight turbidity). They are too small to be measuredby the electron microscope method and are less than 5 millimicronsaverage diameter.

The heel was heated to C. Solutions of sodium silicate and sulfuric acidwere added simultaneously at a uniform rate over a period of two hours.The sodium silicate solution contained 10% SiOz and had a molarSiOzzNazO ratio of 3.36. Enough 4% sulfuric acid solution (approximatelyequal in volume to the sodium silicate solution) was added so that 80%of the NazO in the silicate solution was neutralized during the additionstep. The addition of silicate and acid was continued until one part ofSiOz had been added for each part of SiOz present in the heel. Duringthe additions the pH of the heel slowly rose from 9 to 10 and was thenmaintained at about 10. Vigorous agitation was employed so that themixing was essentially instantanesiliceous substrate for the preparationas follows:

ous. The sodium ion concentration remained below 0.3 N throughout theprocess. This comprises the buildup step.

During the heating of the heel and the subsequent addition of silicateand acid, the tiny, discrete particles of the heel increase in size andthen become chemically bound together in the form of open networks orcoherent aggregates of supercolloidal size wherein the colloidalparticles are present as dense ultimate units. The aggregates areprecipitated.

To aid filtration, the slurry was further fiocculated with a 2% solutionof a mixture of cetyl and lauryl trimethylammonium bromide, 0.16% of themixed compounds being added, based on the weight of the silica. Theslurry was filtered and the wet filter cake reslurried in water. Thereslurry was adjusted to about pH 7 with dilute sulfuric acid, and thenfiltered and the filter cake washed with water. The filter cake,obtained on a vacuum filter, contained about 12.5% by weight of SiOz.

A wet cake of precipitated, reinforced coherent aggregates prepared asjust described and having a specific surface area of 310 m. g. wasesterified in the following manner to make an estersil:

Twenty-two hundred fifty grams of the wet cake containing about 300grams of SiOz was slurried in 6 liters of normal butanol. The slurry wasthen dehydrated by azeotropic distillation, the maximum temperaturereached in the distilling flask being 116.5 C. and the total operationaltime for this step of the process being about 13 hours. The slurry wasthen transferred to a 3-gallon stainless steel autoclave and was heatedto 225 C. under autogeneous pressure. Theheating cycle required about2%. hours after which the autoclave was cooled to room temperature. Thefinal water content in the alcohol phase of slurry was 0.20%. Theproduct was then filtered, the filter cake dried on a steam bath toremove practically all of the free butanol, and finally dried at 75 C.in a vacuum oven for 24 hours.

The dry organophilic and hydrophobic product had a specific surface areaof 269 mF/g. and showed no adsorption of methyl red dye. Chemicalanalysis revealed that the product contained 6.32% carbon and 88.2%SiOz. There were 270 butoxy groups per square millimicrons of surfacearea of the internal structure. The bulk density was 0.101 g./cc. at 3p. s. i. above atmospheric pressure.

One hundred twelve grams of the n-butanol esterified s l ca describedabove was dispersed in 688 grams of a sihcone oil (DC 200, having aviscosity of 100 centistokes at 25 C., produced by the Dow-CorningCorporation), and the mixture was mixed by the silica into the oil inmixture was fairly homogeneous and then passing the resultant greasethrough a Kent 3-roll (4-inch by IO-inch rolljs) ink mill, with therolls set for a clearance of 0.0015 1116 product with a consistency of74 as determined at 77 F. A. S. T. M. micropenetration method (A. S. T.M. Bulletin No. 147, August 1947, pages 81-85). In a heat stabilitytest, a sample of the material heated at 300 F.

ture stability. The grease remained excellent in appearance andconsistency after a standard humidity test which was carried out asfollows:

A sand-blasted 2 x 4" mild steel panel was covered with about a ,5 thickcoating of the grease and was suspended in a humidity box at 100%relative humidity F. for 150 hours. The grease was then examined forclarity, water adsorption, separation of silica, evidences of attack.The metal was also examined for evidences of corrosion.

It was found that the grease remained excellent in appearance andconsistency after this test and was thus highly water resistant.

Example 2.-A hydrophobic estersil was prepared as follows:

pounds of a sodium silicate solution contarmng 2.39 grams SiOz per 100milliliters of solution and having a molar SiOzZNazO ratio of 3.25:1 wascharged to a 100-gallon steel tank equipped with a one-half horsepower400 R. P. Lightnin mixer driving a diameter, 3-bladed propellor. Thesilicate was heated to a temperature of 35:2 C. by steam injection. Asufiicient amount (about 162 pounds) of a solution containing 2.40%H2804 was added uniformly over a period of about 30 minutes to bring thepH to 9.7:02 as measured at 25 C. During this period, the temperature ofthe reacting mass was maintained below 40 C The clear sol thus obtainedwas heated to 95 C. over about minutes.

Solutions of sodium silicate and sulfuric acid were then addedsimultaneously at a uniform rate over a Eighty-five and foursodiumsilicate solution were used, which contained 13.22 grams of SiOz per 100milliliters of solution and had a molar SiOzzNazO ratio of 3.25:1. Thesulfuric acid was 4.65 aqueous solution and was added in an amount tomaintain the pH of the reaction mixture at 10.322 at 25 C. throughoutthe course of the reaction. Such an amount is suflicient to neutralizeabout 80% of the NazO in the silicate solution and main- The temperaturewas main- C. throughout the addition of acid and silicate.

Still maintaining a temperature of 95 C., the pH of the solution wasadjusted from 10.3 to 5.0 by adding 4.65% sulfuric acid at a rate ofabout 0.24 gallon per minute for minutes and then adding small portionsfollowed by repeated pH determinations until the pH was 5 at C. Thisrequired about 32 pounds of the sulfuric acid solution.

he slurry thus obtained was then maintained at 85-95 C. withoutagitation for 16 hours in order to coagulate the precipitate to aid infiltration. The precipitate was filtered in several portions on aSO-gallon Nutsche, using nylon cloth as a filter medium. The filter cakewas washed on the filter with 5 displacements of cold water, and thensucked as dry as possible. The final filter cake contained between 6 and7% solids.

The washed filter cakes were then combined and sufficient normal butanolwas slurried with the wet cake to give a normal butanol-water azeotropeplus sufiicient excess butanol to leave a slurry containing 9 to 10%solids after complete water removal. This mix was then charged to astill for azeotropic dehydration.

The portion of polysiloxane was varied. The

still consisted of a 75-gallon reboiler, a 20, 6" diameter column packedwith /2" Raschig rings, an overhead returned the butanol h upper layerto the column as reflux and separated e heavier water-rich layer. Theslurry was then dehydrated azeotroplcally until the water content of theslurry was below 0.1% by Fischer analysis, and actually around 0.05%.

The butanol slurry was then transferred in 20-22# portions to a 4-gallonnickel stirred autoclave and heated to 290-300 C. under autogenouspressure. The heatup required about 3 hours. The temperature was thenmaintained at 290-300 C. for 15-20 minutes and cooled rapidly to belowC. over 15-30 minutes.

The slurry was removed from the autoclave and dried in a vacuum oven atC. and 10-20, mm. Hg pressure until the silica reached constant Weight.Three separate precipitation and azeotropic dehydration batches wereprepared as above described and esterified in the autoclave in 25separate batches. All of the resultant material was then blended to givea homogeneous sample which was a fluffy white powder and wasorganophilic and hydrophobic. It had a specific surface area of 260 m./g. Analysis showed that the product contained carbon, whichcorresponded to 370 butyl ester groups per 100 sq. millimicrons ofsilica surface.

grease was made from the hydrophobic estersil At the end of thisexposure the grease considerably through oxidation of the but had notthinned out. A portion of this heated grease was also placed in boilingwater and F. for six days. had darkened Further, an unesterified, finelydivided silica was prepared as follows: A portion of a washed wet filtercake prepared in the same manner as described above for the preparationof the hydrophobic estersil was mixed with 3.2 volumes of acetone,stirred mechanically for 1 hour, and filtered on a Nutsche filter undervacuum. This process was repeated two more times using the same ratio offilter cake to acetone. After the third filtration the acetone-Wet cakecontained 3.2% water as determined by titration with Fischer reagent.The cake was then dried in a vacuum oven at 110 C. until no odor ofacetone could be detected. The product was a white, hydrophilic powder.It had a specific surface area by nitrogen adsorption of 337 m. /g., anda hydroxylated surface area by methyl red dye adsorption of 334 m. /g.Thirteen and three-tenths parts by weight phenylsiloxane of mediumaromaticity (DC-550), and 81.7 parts by Weight of the Mid-Continentsolvent treated petroleum oil were compounded by the same method toobtain a lubricating grease. This grease disintegrated almostimmediately in cold Water, with a clean separation of the silica andoil.

Examples 3-14.-Greases were prepared exactly as described in Example 2,except that the type and pro-. details of the preparation of theseexamples, as well as their resistance wen 1n the following table:

that it is preferentially wetted water mixture, the proportion ofsilicone oil in the comby butanol in a butanol- Hydrophobic estersil ofEx- Polysiloxane Employed Polymethylphonyl siloxane (med. aromaticity)Vise. about 59.3 cs. at 100 F (D O-550).

6 tlo Polytnothylsiloxano viscosity about 100 t-s. at

100 F. (DC-200).

10 .do 11 Polymethylphenyl siloxano (high aroinaticity) viscosity about117 cs. at 100 F. (DC-710R).

I claim: l. A composition COmpIlslIlg an estersil and a siliconesupercolloidal substrate coated with OR groups, the substrate having asurface 0 silica and having a specific surface area of from 1 to 900square meters per gram, the coating of --OR groups being chemicallybound to said silica, R being a hydrocarbon radical of from 2 to 18carbon atoms wherein the carbon atom attached to oxygen is also attachedto hydrogen, the estersil being organophilic in that it ispreferentially wetted by butanol in a butanol-water mixture, theproportion of silicone oil in the composition being, by weight, at least1 part per 100 parts of estersil for each 100 square meters of surfacearea per gram of estersil, and the estersil being present in an amountat least sufiicient to increase the viscosity of the composition.

2. A composition comprising an estersil, a silicone oil, and anotherwater-insoluble lubricating oil, said estersil being a supercolloidalsubstrate coated with -OR groups, the' substrate having a surface ofsilica and having a specific surface area of from 1 to 900 square metersper gram, the coating of OR groups being chemically bound to saidsilica, R being a hydrocarbon radical of from 2 to 18 carbon atomswherein the carbon atom attached to oxygen is also attached to hydrogen,the estersil being organophilic in that it is preferentially wetted bybutanol in a butanol-water mixture, the proportion of silicone oil inthe composition being, by weight, at least 1 part per 100 parts ofestersil for each 100 square meters of surface area per gram ofestersil, and the estersil being present in an amount at leastsufficient to increase the viscosity of the composition.

3. A composition comprising a silicone oil and an estersil, saidestersil being a supercolloidal substrate coated with -OR groups, thesubstrate having a surface of silica and having a specific surface areaof from 200 to 900 square meters per gram, the coating of OR groupsbeing chemically bound to said silica, R being a hydrocarbon radical offrom 2 to 18 carbon atoms wherein the carbon atom attached to oxygen isalso attached to hydrogen, the estersil being organophilic in that it ispreferentially wetted by butanol in a butanol-water mixture, theproportion of silicone oil in the composition being, by weight, at least1 part per 100 parts of estersil for each 100 square meters of surfacearea per gram of estersil, and the estersil being present in an amountat least sufiicient to increase the viscosity of the composition.

4. A composition comprising a silicone oil and an estersil, saidestersil being a supercolloidal substrate coated with -OR groups, thesubstrate having a surface of silica and having a specified surface areaof from 200 to 400 square meters per gram, the coating of -OR groupsbeing chemically bound to said silica, R being a hydrocarbon radical offrom 2 to 18 carbon atoms wherein the carbon atom attached to oxygen isalso attached to hydrogen, the estersil being organophilic in oil, saidestersil being a Parts by weight: of:

------''* Micropen. of Grease Days before Complete Mineral at 77 F.disintegrationlnboll- Polyon of after Inking water C.) stloxane ample 2milling 5.0 81.7 71 90. 1. 7 85. 0 71 18 (test stopped). 1.0 85.7 73 70.0.5 86.2 75 15-30 (gradually disintegrated). 0.1 86.6 76 4. 1.7 85.0 7260.

1.0 35.7 70 60. 0. 5 80.2 70 15-25 (gradually disintegrated). 0.1 86.669 4-5. 1.7 85.0 70 60. 1.0 85.7 09 7-15 (gradually disintegrated). 0.586.2 60 4-5. 0.1 86.6 68 3-4.

n position being, by weight, at least 1 part per 100 parts of estersilfor each 100 square meters of surface area per gram of estersil, and theestersil being present in an amount at least sulficient to increase theviscosity of the composition.

5. A lubricating composition comprising an estersil and a silicone oil,said estersil being a supercolloidal substrate coated with -OR groups,the substrate having a surface of silica and having a specific surfacearea of from 1 to 900 square meters per gram, the coating of OR groupsbeing chemically bound to said silica, R being a hydrocarbon radical offrom 2 to 18 carbon atoms wherein the carbon atom attached to oxygen isalso attached to hydrogen, the estersil being organophilic in that it ispreferentially wetted by butanol in a butanolwater mixture, theproportion of silicone oil in the composition being, by weight, at least1 part per 100 parts of estersil for each 100 square meters of surfacearea per gram of estersil, and the estersil being present in an amountat least sufiicient to increase the viscosity of the composition.

6. A composition comprising a silicone oil and an estersil, saidestersil being a supercolloidal substrate coated with -OR groups, thesubstrate having a surface of silica and having a specific surface areaof from 200 to 400 square meters per gram and being coated with at least200 --OR groups per 100 square millimicrons of substrate surface area,the coating of -OR groups being chemically bound to said silica, R beinga hydrocarbon radical of from 2 to 18 carbon atoms wherein the carbonatom attached to oxygen is also attached to hydrogen, the estersil beingorganophilic in that it is preferentially wetted by butanol in abutanol-water mixture, the proportion of silicone oil in the compositionbeing, by weight, at least 1 part per 100 parts of estersil for each 100square meters of surface area per gram of estersil, and the estersilbeing present in an amount at least sufficient to increase the viscosityof the composition.

7. A composition comprising a silicone oil and an estersil, saidestersil being a supercolloidal substrate coated with --OR groups, thesubstrate having a surface of silica and having a specific surface areaof from 1 to 900 square meters per gram and being coated with at least200 -OR groups per 100 square millimicrons of substrate surface area,the coating of -OR groups being chemically bound to said silica, R beinga hydrocarbon radical of from 2 to 18 caron atoms wherein the carbonatom attached to oxygen is also attached to hydrogen, the estersil beingorganophilic in that it is preferentially wetted by butanol in abutanol-water mixture, the proportion of silicone oil in the compositionbeing, by weight, at least 1 part per 100 parts of estersil for each 100square meters of surface area per gram of estersil, and the estersilbeing present in an amount at least sufiicient to increase the viscosityof the composition.

8. A composition comprising a silicone oil and an estersil, saidestersil being a' supercolloidal substrate coated with --OR groups, thesubstrate having a surto 400 square at least 270 11. A compositioncomprising a silicone oil and an estersil, said estersil being asupercolloidal substrate of porous, amorphous silica coated with -ORgroups, the substrate having an average pore diameter of at least 4millimicrons and a specific surface area of from 200 to 900 squaremeters per gram and being coated with at least 270 OR groups per 100square millimicrons of substrate surface area, the coating of -OR groupsbeing chemically bound to said silica, R being a hydrocarbon radical offrom 2 to 18 carbon atoms wherein the carbon atom attached to oxygen isalso attached to hydrogen, the proportion of silicone in the compositionbeing, by weight, from 1 to parts per 100 parts of estersil per m. /g.of estersil surface area, and the estersil being present in an amount atleast sufficient to increase the viscosity of the composition.

12. A composition comprising a silicone oil and an estersil, saidestersil being a supercolloidal substrate coated with a sufiicientnumber of -OR groups to make it hydrophobic, the substrate and greaseconsisting essentially of a silicone oil and a sufiicient proportion ofan estersil to thicken the oil to a grease consistency, said estersilbeing a supercolloidal substrate coated with OR groups, the substratehaving a surface of silica and having a specific increase the viscosityof the composition,

15. A lubricating composition comprising a silicone oil, anotherwater-insoluble lubricating oil, and an estersil, said estersil being asupercolloidal substrate coated with -OR groups, t e substrate having asurface of least 1 part per 100 parts square meters of surface area Noreferences cited.

having a surface of silica I

1. A COMPOSITION COMPRISING AN ESTERSIL AND A SILICONE OIL, SAIDESTERSIL BEING A SUPERCOLLOIDAL SUBSTRATE COATED WITH -OR GROUPS, THESUBSTRATE HAVING A SURFACE OF SILICA AND HAVING A SPECIFIC SURFACE AREAOF FROM 1 TO 900 SQUARE METERS PER GRAM, THE COATING OF -OR GROUPS BEINGCHEMICALLY BOUND TO SAID SILICA, R BEING A HYDROCARBON RADICAL OF FROM 2TO 18 CARBON ATOMS WHEREIN THE CARBON ATOM ATTACHED TO OXYTEN IS ALSOATTACHED TO HYDROGEN, THE ESTERSIL BEING ORGANOPHLIC IN THAT IT ISPREFERENTIALLY WETTED BY BUTANOL IN A BUTANOL-WATER MIXTURE, THEPROPORTION OF SILICONE OIL IN THE COMPOSITION BEING, BY WEIGHT, AT LEAST1 PART PER 100 PARTS OF ESTERSIL FOR EACH 100 SQUARE METERS OF SURFACEAREA PER GRAM OF ESTERSIL, AND THE ESTERSIL BEING PRESENT IN AN AMOUNTAT LEAST SUFFICIENT TO INCREASE THE VISCOSITY OF THE COMPOSITION.